2219 results about "Multiple quantum" patented technology

A semiconductor sensor, solar cell or emitter, or a precursor therefor, has a substrate and one or more textured semiconductor layers deposited onto the substrate. The textured layers enhance light extraction or absorption. Texturing in the region of multiple quantum wells greatly enhances internal quantum efficiency if the semiconductor is polar and the quantum wells are grown along the polar direction. Electroluminescence of LEDs of the invention is dichromatic, and results in variable color LEDs, including white LEDs, without the use of phosphor.

A vertical-cavity surface-emitting laser (VCSEL) comprising a low-loss thin metal contact and current spreading layer within the optical cavity that provides for improved ohmic contact and lateral current distribution, a substrate including a plano-concave optical cavity, a (Ga,In,Al)N multiple quantum well (MQW) active region contained within the optical cavity that generates light when injected by an electrical current, and an integrated micromirror fabricated onto the substrate that provides for optical mode control of the light generated by the active region. A relatively simple process is used to fabricate the VCSEL.

Disclosed is a semiconductor light-emitting element, comprising an n-type-cladding layer; a light guide layer positioned on the n-type cladding layer; a multiple quantum well structure active layer positioned on the light guide layer; a p-type carrier overflow prevention layer positioned on the active layer and having an impurity concentration of 5×10¹⁸ cm⁻³ to not more than 3×10¹⁹ cm⁻³; a p-type light guide layer positioned on the p-type carrier overflow prevention layer and-having an impurity concentration of 1×10¹⁸ cm⁻³ or more and less-than that of the p-type carrier overflow prevention layer; and a p-type cladding layer positioned on the p-type light guide layer and having a band gap narrower than the p-type carrier overflow prevention layer, and a method of manufacturing the same.

A method of slice selective multiple quantum magnetic resonance imaging of an object is disclosed. The method is effected by implementing the steps of (a) applying a radiofrequency pulse sequence selected so as to select a coherence of an order n to the object, wherein n is zero, a positive or a negative integer other than ±1; (b) applying magnetic gradient pulses, so as to select a slice of the object to be imaged arid to create an image; and (c) acquiring a radiofrequency signal resulting from the object, so as to generate a magnetic resonance slice image of the object. The method provides slice selective multiple quantum magnetic resonance images of yet unprecedented quality in terms of contrast. The method is particularly useful for imaging connective tissues.

The present invention is a semiconductor structure for light emitting devices that can emit in the red to ultraviolet portion of the electromagnetic spectrum. The structure includes a first n-type cladding layer of Al_xIn_yGa_1−x−yN, where 0≦x≦1 and 0≦y<1 and (x+y)≦1; a second n-type cladding layer of Al_xIn_yGa_1−x−yN, where 0≦x≦1 and 0≦y<1 and (x+y)≦1, wherein the second n-type cladding layer is further characterized by the substantial absence of magnesium; an active portion between the first and second cladding layers in the form of a multiple quantum well having a plurality of In_xGa_1−xN well layers where 0<x<1 separated by a corresponding plurality of Al_xIn_yGa_1−x−yN barrier layers where 0≦x≦1 and 0≦y≦1; a p-type layer of a Group III nitride, wherein the second n-type cladding layer is positioned between the p-type layer and the multiple quantum well; and wherein the first and second n-type cladding layers have respective bandgaps that are each larger than the bandgap of the well layers. In preferred embodiments, a Group III nitride superlattice supports the multiple quantum well.

A method of manufacturing a solar cell by providing a first semiconductor substrate for the epitaxial growth of semiconductor material; forming a first subcell on the substrate with a first semiconductor material with a first band gap and a first lattice constant; forming a second subcell with a second semiconductor material with a second band gap and a second lattice constant, wherein the second band gap is less than the first band gap and the second lattice constant is greater than the first lattice constant; the second subcell including a strain balanced quantum well structure; and forming a lattice constant transition material positioned between the first subcell and the second subcell, the lattice constant transition material having a lattice constant that changes gradually from the first lattice constant to the second lattice constant.

The present invention discloses a double-reflective-layer gallium nitride-based flip-chip light-emitting diode with both a distributed Bragg reflector and a metal reflective layer on its side and a fabrication method thereof. The light-emitting diode includes: a sapphire substrate; a buffer layer, an N-GaN layer, a multiple-quantum-well layer and a P-GaN layer stacked on the sapphire substrate in that order; a transparent conductive layer formed on the P-GaN layer; a distributed Bragg reflector formed over a side of the epitaxial layer and the transparent conductive layer; a metal reflective layer formed on the DBR; a P-type ohmic contact electrode formed on the transparent conductive layer; and an N-type ohmic contact electrode formed on the exposed N-GaN layer, wherein the P-type ohmic contact electrode and the N-type ohmic contact electrode are bonded to a heat dissipation substrate through a metal conductive layer and a ball bonder. By arranging a double reflection structure including a DBR and a metal reflective layer on the sloping side of the LED chip, the good reflectivity of the reflective layers can be fully utilized, thereby improving the light-emission efficiency of the LED.

The invention relates to GaN-based Single chip white light emitting diode epitaxial material comprising a substrate and also comprising an initial growth layer, an intrinsic GaN buffer layer, an n-type GaN layer, a stress relaxation layer, an InGaN multiple quantum well structure light emitting layer, a p-type AlGaN sandwich layer and a p-type GaN layer which grow in sequence on the substrate. Thestress relaxation layer is an InGaN/GaN superlattice stress modulation layer which comprises InGaN layers and GaN layers, which are grown alternatively; the InGaN layers and GaN layers have the growth cycle of 6-500 and the corresponding thickness of 10 nm to 3 Mum; and the In components in the InGaN layers are in the range of 1-35 percent. Because the stress-relaxed InGaN/GaN superlattice stressmodulation layer is added between the n-type GaN layer and a multiple quantum light emitting layer, the In segregation effect is strengthened, InGaN quantum dots with different components are formed,and the mixing of different-wave light emitted by the InGaN quantum dots realizes the white light emitting. The cost of the white light emitting diode is reduced radically, the light emitting efficiency and the light using efficiency are increased and the integral performance of the white light emitting diode is improved.

The present invention is a tunable semiconductor laser for swept source optical coherence tomography, comprising a semiconductor substrate; a waveguide on top of said substrate with multiple sections of different band gap engineered multiple quantum wells (MQWs); a multiple of distributed feedback (DFB) gratings corresponding to each said band gap engineered MWQs, each DFB having a different Bragg grating period; and anti-reflection (AR) coating deposited on at least the laser emission facet of the laser to suppress the resonance of Fabry-Perot cavity modes. Each DFB MQWs section can be activated and tuned to lase across a fraction of the overall bandwidth as is achievable for a single DFB laser and all sections can be sequentially activated and tuned so as to collectively cover a broad bandwidth, or simultaneously activated and tuned to enable a tunable multi-wavelength laser. The laser hence can emit either a single lasing wavelength or a multiple of lasing wavelengths and is very suitable for swept-source OCT applications.

A Mach-Zehnder type optical modulator having a ridge structure including a multiple quantum well wave guide layer expending both in a passive region and in an active phase modulation region on which an electrical field is applied, wherein the wave guide layer is selectively grown by a metal organic vapor phase epitaxy with use of dielectric stripe mask patterns having a large width in the active phase modulation region and a small width in the passive region so that the wave guide layer has a band gap wavelength equal to or near a wavelength of an incidental light in the active phase modulation region and a smaller band gap wavelength smaller than the wavelength of the incidental light in the passive region.

The invention discloses a method for enhancing the antistatic ability of GaN-based light-emitting diode. The epitaxial wafer structure of the light-emitting diode sequentially comprises an underlay, alow-temperature buffer layer, an unadulterated GaN high-temperature buffer layer, an aluminum gallium nitride/ GaN superlattice structure, the unadulterated GaN high-temperature buffer layer, an N type contact layer, an N type GaN conductive layer, a light-emitting layer multiple quantum well structure MQW, a P type aluminum gallium nitride electric barrier layer, a P type GaN conductive layer and a P type contact layer in a sequence from down to up. In the invention, the aluminum gallium nitride/ GaN superlattice periodic structure is inserted in the unalloyed GaN high temperature buffer layer. The insertion of the aluminum gallium nitride/ GaN superlattice periodic structure can effectively improve crystal quality of materials, thereby enhancing the antistatic ability of the GaN-based light-emitting diode and improving the reliability and the stability of devices.

Disclosed is a light emitting diode (LED) having an active region of a multiple quantum well structure in which well layers and barrier layers are alternately laminated between a GaN-based N-type compound semiconductor layer and a GaN-based P-type compound semiconductor layer. The LED includes a middle barrier layer having a bandgap relatively wider than the first barrier layer adjacent to the N-type compound semiconductor layer and the n-th barrier layer adjacent to the P-type compound semiconductor layer. The middle barrier layer is positioned between the first and n-th barrier layers. Accordingly, positions at which electrons and holes are combined in the multiple quantum well structure to emit light can be controlled, and luminous efficiency can be enhanced. Furthermore, an LED is provided with enhanced luminous efficiency using a bandgap engineering or impurity doping technique.

A GaN/AlN superlattice is formed over a GaN/sapphire template structure, serving in part as a strain relief layer for growth of subsequent layers (e.g., deep UV light emitting diodes). The GaN/AlN superlattice mitigates the strain between a GaN/sapphire template and a multiple quantum well heterostructure active region, allowing the use of high Al mole fraction in the active region, and therefore emission in the deep UV wavelengths.

The present invention provides a nitride semiconductor light emitting device with an active layer of the multiple quantum well structure, in which the device has an improved luminous intensity and a good electrostatic withstanding voltage, thereby allowing the expanded application to various products. The active layer 7 is formed of a multiple quantum well structure containing In_aGa_1−aN (0≦a<1). The p-cladding layer 8 is formed on said active layer containing the p-type impurity. The p-cladding layer 8 is made of a multi-film layer including a first nitride semiconductor film containing Al and a second nitride semiconductor film having a composition different from that of said first nitride semiconductor film. Alternatively, the p-cladding layer 8 is made of single-layered layer made of Al_bGa_1−bN (0≦b≦1). A low-doped layer 9 is grown on the p-cladding layer 8 having a p-type impurity concentration lower than that of the p-cladding layer 8. A p-contact layer is grown on the low-doped layer 9 having a p-type impurity concentration higher than those of the p-cladding layer 8 and the low-doped layer 9.

Layered and film structures for improving the performance of semiconductor devices include single and multiple quantum wells and double heterostructures and superlattice structures.

It is an object of the present invention to provide a semiconductor laser device with high-yielding in which a clack generated in an epitaxial growth layer is restrained and to the manufacturing method thereof, the semiconductor laser device includes a GaN substrate 1, an n-type GaN layer 2, an n-type AlGaN cladding layer 3, a n-type GaN guide layer 4, an InGaN multiple quantum well active layer 5, an undoped-GaN guide layer 6, a p-type AlGaN electron overflow suppression layer 7, a p-type GaN guide layer 8, a SiO₂ blocking layer 9, an Ni/ITO cladding layer electrode 10 as a transparent electrode, a Ti/Au pad electrode 11, and a Ti/Al/Ni/Au electrode 12. The SiO₂ blocking layer 9 is formed above the InGaN multiple quantum well active layer 5 so as to have an opening. The Ni/ITO cladding layer electrode 10 is formed inside the opening, and which is transparent for the light from the InGaN multiple quantum well active layer, and serves as a cladding layer.

A semiconductor light emitting device including means for reducing strain and carrier overflow caused by injection of a number of carriers in semiconductor light emitting devices using GaN is provided. The semiconductor light emitting device includes a multi-quantum barrier formed by depositing an AlGaN/GaN double layer a predetermined number of times, or a strain-compensating multiple quantum barrier formed at either the upper or lower sides of an active layer by depositing an AlGaN/InGaN double layer a predetermined number of times, and does not need a p-type clad layer.

The invention discloses a surface roughening method of a p-GaN layer or an ITO layer in a GaN-based LED chip structure. The method comprises the following steps: (1) growing a low-temperature GaN buffer layer, an undoped GaN layer, an n-GaN layer, a multiple quantum well layer, a stack-up structure of the p-GaN layer and an extended layer evaporating ITO current on a semiconductor substrate in sequence; and (2) preparing monolayer nickel nano particles as a mask, and preparing a roughening structure on the p-GaN layer or the ITO layer. The method of the invention has simple steps, low cost, good roughening effect; by carrying out surface roughening on the p-GaN layer or the ITO layer of the GaN-based LED by the method of the invention, the total reflection of the photon in the chip can be inhibited and the light outgoing efficiency of the devices can be improved.

Conductivity-selective lateral etching of III-nitride materials is described. Methods and structures for making vertical cavity surface emitting lasers with distributed Bragg reflectors via electrochemical etching are described. Layer-selective, lateral electrochemical etching of multi-layer stacks is employed to form semiconductor/air DBR structures adjacent active multiple quantum well regions of the lasers. The electrochemical etching techniques are suitable for high-volume production of lasers and other III-nitride devices, such as lasers, HEMT transistors, power transistors, MEMs structures, and LEDs.

A surface treated nitride semiconductor in use for a light emitting diode, in which an n-cladding layer is formed on a substrate. An active layer having a multiple quantum well structure is formed on the n-cladding layer. A p-cladding layer is formed on the active layer. A p-capping layer is formed on the p-cladding layer in a low temperature range in which single crystal growth does not take place. The p-capping layer has a nanoscale roughened structure formed in an upper surface thereof via heat treatment in a high temperature range in which at least partial crystallization takes place. The nanoscale roughened structure reduces total internal reflection of the nitride semiconductor thereby improving external quantum efficiency thereof.